A hydraulically driven tube reaming machine such as that shown in my U.S. Pat. No. 4,105,304 includes a cutterhead mounted on a drive shaft that is somewhat longer than the set of tubes that are to be reamed. Thus, the working space that is required for the machine, adjacent to the heat exchanger, is longer than the heat exchanger itself.
A technique has heretofore been developed for using a machine of fixed length for reaming heat exchanger tubes of different lengths. For example, the machine is constructed of such length as to ream tubes that are 30 feet long. When another set of tubes are to be reamed that are, for example, 15 feet in length, an internal modification is made in the machine to shorten the effective length of its drive cylinder. Thus the machine itself is still 30 feet long plus an additional distance that is required to support the drive shaft, but the working stroke of the drive shaft has been diminished by 15 feet. Of course this type of modification cannot be used at all if the available machine is only 15 feet long and the heat exchanger tubes to be reamed are of a greater length than that.
It sometimes happens that a heat exchanger which is, for example, 15 feet in length has sufficient space adjacent to it to install a reaming machine of the necessary size, but the shape is not large enough to install a bigger reaming machine. In actual practice this has necessitated providing, and transporting to the work location such as an oil refinery, several different reaming machines even though there is only a single crew to operate them. A separate reaming machine or a corresponding size has been required for each size of heat exchanger. A particular reaming machine does not have sufficient reach to operate on a heat exchanger that is longer than what it was designed for. And where the heat exchanger is shorter than what the machine is designed for, the working space beside the heat exchanger may not be sufficient to accommodate the machine. Hence the practical requirement that a single crew must be equipped with several different machines, one for each size of heat exchanger.
When oil refineries are being cleaned and repaired the shut down time is a crucial factor. It is desirable to accomplish the necessary maintenance work such as reaming the heat exchanger tubes in an absolute minimum amount of time. Otherwise the productive capacity of the refinery that is lost can amount to a great deal of money. Hence it is essential that crews who operate tube reaming machines for the necessary maintenance and reconditioning of refinery heat exchangers must be provided with equipment that is efficient and reliable and can be operated at maximum speed.